1. Field of the Invention
The present invention generally relates to a socket connector for mounting an electronic device, such as a central processing unit (CPU) module, to a circuit board, and more particular to a contact of the socket connector having a cost- and material-saving structure.
2. The Related Arts
Socket connectors for mounting an electronic device, such as a central processing unit (CPU) module, to a circuit board are well known and commonly used in the computer industry. FIG. 1 of the attached drawings shows an example of the socket connectors that is referred to as ZIF (Zero Insertion Force) socket connector. The socket connector, generally designated with reference numeral 10, comprises a base or housing 12 defining an array of open cells 14 in which contacts (not shown in FIG. 1) are received and a cover 16 movably supported on the base 12. The cover 16 defines through holes 18 corresponding to the cells 14 of the base 12. The cover 16 is capable to carry a CPU module 20 with pin legs 22 of the CPU module 20 extending through the holes 18 of the cover 16 and partially into the cells 14. An actuator 24 drives the cover 16 in such a manner to bring the pin legs 24 of the CPU module 20 into contact with the contacts of the base 12 thereby forming electrical connection therebetween. Examples of socket connectors of this type are also disclosed in U.S. Pat. Nos. 4,498,725, 5,833,483, 6,059,596, 6,142,810, and 6,159,032.
FIG. 2 of the attached drawings shows a contact, designated with reference numeral 26, received in each of the open cells 14 of the base 12 of the conventional socket connector 10. The contact 26 is made by stamping a metal plate as shown in FIG. 3. The contact 26 comprises a flat body 28 interferentially fit in the cell 14, two spring arms 30 which are bent from the flat body 28 to be substantially opposite to each other and a solder pad 32 also bent from the flat body 28 to be substantially perpendicular thereto for carrying a solder ball (not shown). As shown in FIG. 3, a number of contact blanks 26xe2x80x2 (that will finally form the contacts 26) are lined up and connected to a carrier strip 34 after the stamping operation. To save material of the metal plate that makes the contacts 26, the contact blanks 26xe2x80x2 are arranged as close to each other along the carrier strip 34. However, the dual spring arm structure of the contact 26 requires that a distance between adjacent contact blanks 26xe2x80x2 be at least as large as twice the span of the spring arm 30 of the contact 26. Practically, such a distance is about 2.54 mm. However, the center-to-center distance between adjacent cells 14 of the connector housing 12 is 1.27 mm, that is half of the distance between adjacent contact blanks 26xe2x80x2 along the carrier strip 34. For each line of the cells 14 of the base 12, a contact fitting process that handles a single carrier strip 34 can only place the contacts 26 into every other ones of the cells 14. Thus to completely fill the line of the cells 14, two contact fitting processes must be performed. This is generally not a time- and cost-efficient manner.
Further, arranging contacts along a carrier strip with a double span between adjacent contacts is a waste of material of the metal plate because a large portion of the material between the flat bodies of adjacent contacts will be stamped away.
Thus, it is an object of the present invention to provide a contact structure wherein contact blanks are arranged along a carrier strip with a single span between adjacent contact blanks so as to enhance assemblage of the contacts in a housing and reduce waste of material.
Another object of the present invention is to provide a contact for a socket connector, the contact having a simplified structure so as to reduces costs of manufacture.
To achieve the above objects, in accordance with the present invention, a contact for a socket connector is provided. The contact is made by stamping a metal plate whereby a number of contact blanks are formed and equally-spaced along a carrier strip that partly constitutes the metal plate. The contact has a single spring arm whereby the distance between adjacent contact blanks along the carrier strips is substantially corresponding to a single arm span, thereby saving material between adjacent contact blanks. The single arm span distance between adjacent contact blanks allows the contacts to be arranged in a more compact fashion along the carrier strip and thus assembling the contacts to a housing can be done more efficiently. Each contact blank comprises an elongate flat body having, at a first end thereof, an enlarged section and, at a second end thereof, a first inclined extension. A second inclined extension projects from a lateral side edge of the flat body and is substantially parallel to the first inclined extension. The enlarged section is attached to the carrier strip by a ready-to-separate connection that allows a finally formed contact to be readily separated from the carrier strip. The flat body has a first major surface. The enlarged section is bent approximately 90 degrees to form a soldering pad substantially perpendicular to the first surface for carrying a solder ball. The first extension is coplanar to the first surface. The second extension is bent at an angle no more than 90 degrees whereby the second extension is inclined with respect to the first surface and a lengthwise direction of the flat body. The contact is fit into a cell defined in a housing with the first extension, functioning as retaining arm, interferentially fit into a slot defined inside the cell to secure the contact in the housing. The second extension, functioning as a spring arm, is arranged to be substantially corresponding to a moving direction of a corresponding pin leg of a central processing unit module. The inclination of the spring arm provides resiliency of the spring arm for firmly engaging the pin leg.